ARMA 2: Der Untergang was a scrapped Downfall parody-themed ARMA 2 Combined Operations mini-mod. It was to add Downfall parody characters to the game, as well as 3 campaigns, focusing on the parody universe. It was also intended to support other mods (eg. Invasion 1944, Unsung: Vietnam War mod, Project '85) as well.
The mod was scrapped because developing a Downfall parody-themed mod for ARMA 2 would take a ludicrously long time; one has to add new voice-chatters. Compared to the previous games, there are about thousands of them for each voice set.